Farshid's Weblog

Relocation of my weblog

harandi — Tue, 15 Feb 2011 19:48:44 +0000

My blog, farshidjh.wordpress.com will be hosted on blog.farshidjh.com on my own domain at farshidjh.com from now on. Please update your bookmarks and correct your records.
Hope you would find my posts useful,
Farshid

How to make a LED bracelet with small LEDs

harandi — Sun, 06 Feb 2011 03:10:26 +0000

Following pictures show different steps of making an LED bracelet with small LEDs and pieces of copper wire. Hover your mouse on top of each of the pictures to see details about that step and click to have a closer look.

How to make a LED bracelet with small 3mm Orange flat top LEDs and thin wires

harandi — Sun, 06 Feb 2011 03:08:28 +0000

Following pictures show different steps of making an LED bracelet with small 3mm orange LEDs and pieces of thin wire. Hover your mouse on top of each of the pictures to see details about that step and click to have a closer look.

How to make a LED bracelet with small 3mm Yellow flat top LEDs and thin brass tubes

harandi — Sun, 06 Feb 2011 02:58:33 +0000

Following pictures show different steps of making an LED bracelet with small 3mm yellow LEDs and pieces of brass tube. Hover your mouse on top of each of the pictures to see details about

12V Lamp on Arduino with a reed relay

harandi — Tue, 18 Jan 2011 08:26:39 +0000

Intro

Arduino has a limited current sinking/sourcing capability (less than 40 mili Amps) on its pins. Whenever you intend to switch a device which needs high current or high voltage (like a lamp or a motor) an intermediate circuit is needed. In the simplest case this intermediate circuit is a relay.

Relays

Relay acts as a normal switch, but is triggered with a magnet rather than a handle. Here we use a special kind of relay called reed relay. Such relays come in vacuum enclosures and have excellent performance in terms of being an ideal switch. Whenever driving coils there should be a diode connected across the coil in reverse bias, so it will damp the back EMF produced. However, the relay we are using has this diode across its coils internally, so we don’t need to worry about it.

Circuit

Make the circuit below:

Select the Blink sketch (File>Examples>Digital>Blink) from your Arduino software and upload it to your board. The Lamp on the bread and the LED on your Arduino board should light up at the same time.

More info

Note that similar to any other load, relays draw current. This current can be more than what an Arduino can provide. In such cases you cannot connect the relay directly to an Arduino output. Use a transistor for the relay and a diode to protect against back EMF. Here is an example how to drive such a relay with a transistor.

An easier approach for driving high current/voltage relays is to use a relay driver such as ULN2003 or ULN2803. Here is a sample schematic how to do so (taken from this rocket project).

‘Micro sequencer’ an Arduino musical instrument

harandi — Tue, 18 Jan 2011 08:15:04 +0000

Introduction

Micro sequencer plays a sequence of 4 randomly chosen tones on Arduino. Tempo (playback speed) and tone length (more like a tremolo) can be controlled via two analog inputs. Four buttons control the octave of the tones where another button is used to generate a new random set of tone sequence. The sequence can be stored in the non volatile memory by pressing another button.

Circuit

The board is shown in the picture above. Its better to build the circuit on a bread board before soldering it on a piece of strip board. The schematics for the micro sequencer is shown below:

As shown above 6 push buttons are used on digital inputs (pull up resistors, R1-R6 can be any value from 1K to 10K ohm) and two potentiometers are on Analog inputs (potentiometers can be any range from 1K to 50K ohm).

If you intend to increase the number of buttons or analog inputs simply copy the same component and connections and change the code accordingly. You can use a variety of sensors (LDRs, IR/Ultra Sonic distance meters, Force sensors, etc.) instead of the potentiometers.

Code

This program uses the tremolo effect that has been developed by Jaxon BK.

Program reads the inputs listed below and plays back a sequence according to the inputs on digital pin 9 of Arduino. The music signal needs to be amplified with a small amplifier like an LM386 amplifier.

Button 1: Generates a new random tone sequence (keep pressing until you hear a beep)

Button 2: Store the sequence to the non-volatile memory (keep pressing until you hear two beeps)

Button 3-6: Holding these button will affect the octave of the tones being played at that moment. (3 Lowest, 4 Low, 5 High, 6 Highest octave)

Analog input 0: Controls the tempo (playback speed)

Analog input 1: Controls the tremolo (similar to length of playback of the note)

The tone values are also printed on serial port of the Arduino board when button 1 or 2 are pressed. So if you would like to see the frequencies you can open the Arduino serial monitor. Saved data will be loaded upon reset. So, each time you power on or reset your Arduino the saved tone sequence will be loaded from the non-volatile memory.

Do not leave the button 2 unconnected! otherwise the program might try writing to the non-volatile memory all the time. Pull these pins high if you do not intend to place a switch in your final circuit.

Download the code from here.

More info

Here is a simple guide to music and music alphabets. Here you can read about mapping of frequency to notes.

A line-follower robot at Valand!

harandi — Fri, 19 Nov 2010 00:06:30 +0000

Introduction:

If you are interested to build a Line Follower robot with an Arduino here is how to do it.

You will need two wheels, two continuous servos as the motor, infra red sensor array, An Arduino board, and some other components that are pictured below:

line follower robot components

Schematics

Here is the schematics for the robot. It’s the best to make the circuit in steps as shown below. When you are finished with the servo circuit you can load the ‘servo test’ provided in the code section.

: Two continuous servos connected to Arduino (line follower rbot)

: Two continuous servos and Pololu QTR-8A and an infra red sensor array connected to Arduino (line follower rbot)

Code

Here are the source codes for your robot. Set up the servos first and use the Servo test code to test to see if you have done everything right. If everything works, connect the Infra red sensor board and upload Line follower code.

When you have the line follower code you can also open the serial monitor of the Arduino program (set the speed to 115200) and watch the sensor output. If everything works fine you can see an output similar to this:

00011000
0

The first line indicates the value that is read from the sensors (left to right represent sensor 1 to sensor 8 respectively ).

Second line print the assigned line position. If the line goes under the sensors 1 the line position will read 7 and in case the line is at the center it will read 0 and finally if line goes under sensor 1, line position will read -7.

List of Components

Wheels:
2 x Servohjul [SRVT-01], 96:-/st of two
http://www.hobbytronik.se/product_info.php/products_id/35

Support Wheel
1 x Stödkula, metall, 9.5 mm [BCP-02] , 24:- / piece
http://www.hobbytronik.se/product_info.php/products_id/152

Sensors:
1 x Multipel reflektsensor, analog [QTR-8A] 104:-/board
http://www.hobbytronik.se/product_info.php/products_id/172
OR
1 x QTR-8A Reflect. Sensor Array [POL-0960] 109:/board
http://www.lawicel-shop.se/shop/

Motors:
2 x Parallax Cont. Rotation Servo [900-00008] , 109:-/each
http://www.lawicel-shop.se/
OR
2 x Servo 360° [41003767] , 149:-/each
http://www.electrokit.se/

Arduino:
1 x Arduino Duemilanove (2009) [ARD-2009] ,
http://www.lawicel-shop.se/
OR
1 x Arduino UNO utvecklingskort (MEGA328) [12200024] ,
http://www.electrokit.se/

Pin headers:
1 x Stiftlist rak 2.54 mm 1×40 pol brytbar [Nr 41001167] , 8:-/each
http://www.electrokit.se

Battery holder:
1 x Battery tray 6 x AAA, 2.035 UM-4 LR03, 30:-/each
http://www.elfa.se

Batteries:
1 x AAA/LR03 [32-6312-10] , 30:-/pack
http://www.elfa.se

Battery snap:
1 x Battery holder 6LR61/9 V 100 mm, BS-IR [42-001-50] , 9.5:-/each
http://www.elfa.se

Prototyping board:
1 x Laboratory strip board [] , :-/each
http://www.elfa.se

DC jack
1 x DC-adapter jack [] , :-/each
http://www.elfa.se

Black Tape:
1 x Svart tejp [36-1975] 29:-/st
http://www.clasohlson.se/

Presentation

You can View or Download find the slides for the first presentation (and the second one) of this robot @ Valand School of fine arts by me as a guest lecture:

Keep me updated about what you do !

Charotor flying outside

harandi — Thu, 25 Mar 2010 17:38:30 +0000

Here is a short update :

Model radio transmitters and HobbyKing 6 Channel transmitter guide

harandi — Mon, 01 Mar 2010 02:24:07 +0000

I believe making a PC based RX/TX is pretty inefficient as you would get used to the controls on a real TX device much sooner than a PC keyboard, so take my advice and buy one. There are two common modes for model airplane/helicopter radio transmitters. The main difference is that the mode 2 transmitters have the throttle on the left stick while mode 1 has it on the right side. Here you can read more about modes of a transmitters.

There are famous brands such as Futaba, Spektrum, JR and also cheaper barnds like FlySky, Turnigy, HobbyKing. Cheaper models mostly share the same board/casing with different labels. Quality is mostly the same. If you would like to stick with cheap transmitters there are two obvious options to choose from as of today.

1. HobbyKing 6 channel 2.4Ghz (Branded as Flysky, iMax and more)

This is a very cheap transmitter sold for 32.95 with the Transmitter unit and receiver unit included. There is another one sold for even a cheaper price at 29.99. I would go for the 6 channel since it can be programmed with a PC USB cable for 2.99 which I highly recommend you to buy. This is a good starter unit if you are not about to use it for only one model. Here is a good review on the 4ch transmitter which is similar in hardware to the 6 channel.

2. Turnigy 9 channel (Also branded as Flysky, iMax and more)

This unit comes for 69.99 without the receiver or the transmitter. You only buy the remote control for this price. you can beef it up with Assan module or Corona module Transmitter and receiver modules. Here is a good review on it. This unit also comes with bundled TX/RX modules for a cheaper price like 109.19 including shipping and there is not much information provided about the bundled TX/RX unit and its quality.

To stay cheap I ordered a HobbyKing 6-ch transmitters. I have had minor problems but got over them all. Thanks to Hari, I followed his guide and used the Turborix software to configure the transmitter.

Quick installation of HobbyKing 6 channel transmitter cable and PC software:

1. Cable driver: UL2102

2. ATeasy 7 runtime files: Ateasy 7-142c

3. Turborix configuration software: Programmer

4. Configuration for my own quad (Mode 2 transmitter): Turborix configuration set

Detailed info:

The biggest issue for me was to get the driver for the USB cable (FreeScale RS232 to USB) to install. The driver provided at Hari’s website didn’t worked for me. I went to Freescale website to find UL2102 (if I recall it correctly) to install the driver.

ATeasy installs the necessary runtime files needed to let you run the Turborix. I had problems installing the ATeasy6 from the given link in Hari’s website. So I visited the original website and installed ATeasy7 which works like a charm with Turborix. Try this first if it does not works goto here (get it from the ‘software pkgs’ at the bottom right side of the page)

Turborix is a replacement software developed thanks to keepitsimple. Since the configuration software, T6 Config, from the original vendor uses ‘Engrish’ I prefer not to use it.

You don’t need 8 AA (~12 Volts) batteries to power this transmitter. This unit needs to be powered by a source greater than 7 V, and anything above 7 Volts will turn into heat. A 12V supply will only produce more heat and has no effect whatsoever on anything like the range. I am using a 2 Cell 1000mAH Lipo (7.4V nominal) as power source. I modified the battery voltage monitoring LED so it will shine correctly. It is a simple matter of paralleling another resistor to the voltage divider resistors (I paralleled a 20K resistor along the 10K one):

FAQ :

How long is the range of this transmitter ?

I have not had made a range test. Remote works indoors from 15 meters with 4 walls in between as obstacles and I never had problems flying outside/inside. Another user at RCgroups reported “The distance is 830 m (2720 ft), just over half a mile. But I must say that this not direct line of sight, because of a row of trees at the west end of the field.” here

Can I power the transmitter with a small 9V battery (rechargeable or not) ?

I wouldn’t recommend that. I have not measured the current consumption of the transmitter, but I believe it has current bursts (momentary demands for high current) during transmission which is ‘not satisfiable’ by a small 9V battery (rechargeable ones that are rated for ~ 200mAH or more ‘may’ last for a very short time). Never risk your transmitter. It is the only thing that relates your hands to your expensive, and potentially harmful flying flying machine of yours.
If you have 8 AA rechargeable batteries lying around you can use them or if you want to look more ‘geek’ buy an extra 2 cell 1000mAH Lipo battery for almost 7$ from Hobbyking and enjoy.

Need more info on how to use T6 Config and sample configuration files ?

You can look here

Need more info and discussions about HobbyKing 4/6 Channel transmitter :

Look here

Hope this helps,
Farshid

Building a Quadrotor – Master thesis

harandi — Wed, 24 Feb 2010 01:48:42 +0000

Charotor the quadrotor flying robot

Here you can find the abstract and first pages of my thesis. It is about a Quadrotor which I earlier started to post about. This robot got me the highest score for my thesis and the robot was sold to the Qazvin Azad University only covering the expenses and nothing more and University demands to keep on the copyright to me.

Expect more information to come about the quadrotor in near future.

Farshid Jafari Harandi ‘s Master Thesis on Building a Quadrotor flying robot

Full text is available in Qazvin Azad university as a thesis and also somewhere in the national library. Please DO NOT ask for the full text in emails, full text is only avaiable throught the mentioned resources.

However, here you can download the full text for the paper I’ve submitted for this project.

Farshid